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Fire-pumps are typically listed by an approval institute and can be driven either by an electric motor or diesel engine. In a fire installation there can be one or more fire pumps put into operation as a duty assist (50%) – and standby pumps.
The fire-pump delivers the water via the pipe-system to the fire sprinklers to suppress the fire. Fire pumps are powered either by an electric motor or a diesel engine or sometimes by a steam turbine. The number of fire-pumps installed depends on the occupancy hazard (LH, OH or HH) and specific fire installation standard. Some known can be seen in the table to the right.
Where twin electric fire pumps are installed, there is a requirement for a secondary power source. This can be from a separate feed to the nearest electricity sub-station, or from a generator located on site. A mains changeover facility should be incorporated into the design to allow for switching to this alternate power source in the event of a mains supply failure.
The fire pump starts when the pressure in the fire sprinkler system drops below a certain set-point. If one or more fire sprinklers are exposed to heat above their design temperature, and opens, the sprinkler system pressure drops and the pressure switches gives a signal and the duty pump starts. If the duty-pump, for any reason, does not start, the standby pump will start, usually from a secondary pressure switch.
Types of pumps used for fire service include: end suction, horizontal split case, vertical split case, vertical inline and vertical turbines. Most fire-pumps are listed for fire pump application, which means they are tested and certified by accredited laboratories and listed by authorized institutions such as UL, FM, and LPCB etc.
When starting a fire pump design, the most important item to consider is the water supply. If you are utilizing the city water supply as the primary source for the pump, you need to make sure that an accurate city water test is used. Some good rules to follow are: